"People who abuse drugs tend to abuse many different drugs, yet much of the current research in the field focuses on single drug abuse," explained primary investigator, Robert Raffa, Ph.D., professor of pharmacology at Temple University School of Pharmacy.
Typically, abusers take several drugs together to multiply the pleasurable effects or manage the undesirable effects-for instance, using alcohol with cocaine. Because each type of drug affects the body differently, withdrawal is more complicated when more than one is involved. It would be impossible to conduct controlled scientific research on human subjects, so scientists have sought out alternatives.
As a study subject, the Planaria worm, a type of flatworm known for its regenerative powers, has several qualities attractive to scientists. First, it has such simple biochemistry and it readily absorbs any chemical in which it is soaked. This simplicity makes it a clean, easy-to-use model. But despite this simplicity, the Planaria worm has a brain and spinal cord, both key to studying the effects of drug abuse and withdrawal. Furthermore, Planaria have the same types of neurotransmitter systems as humans and thus respond to dopamine, opioids, cocaine and cannabinoids.
"Planaria offer a clean and uncomplicated model. We don't have to worry about potential interference from other organs or organ systems, as would be the case in other animal models," said Raffa. "Plus, Planaria display amazing behaviors. They can even learn."
Some might remember Planaria from biology experiments in grade school. According to Raffa, the worm was a popular research model in the 1960s, but hasn't been used much since. Because of its many advantages, however, he predicts they might experience a resurgence of use in scientific research over the next couple of years.
Before Raffa entered academia, he was a scientist at Johnson & Johnson, where he conducted important work on the analgesic drug Tramadol. Today, he continues to study analgesics, with a current project looking at how acetaminophen produces its effects. Through pharmacology, he combines his interests in math, engineering and the brain. His primary interest is in figuring out how drugs work and produce their effects.
Raffa is collaborating on this NIH study with Ronald Tallarida, Ph.D., professor of pharmacology at Temple's School of Medicine and Vice Provost for Faculty Affairs.